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BJU earth science c3
BJU Press space and earth science chapter 3
| Question | Answer |
|---|---|
| Right ascension | Celestial longitude; measured in hours, minutes, and seconds east of the prime hour circle (p. 66) |
| declination (DEC) | Celestial latitude. Angular distance north or south of the celestial equator measured in degrees ( p. 66) |
| Eclipsing Binary | Two stars revolving around each other such that they periodically pass in front of each other relative to the observer (p. 72) |
| Red Star shift | a mathematical rule for measuring distances to stars and galaxies that relates the stretching of wavelengths of their light with increasing distances (p. 69) |
| negative magnitude | The brightest stars have negative magnitude (magnitude is determined by the amount of light a star emits and its distance from earth) (p. 68) |
| positive magnitude | Fainter stars are said to have positive magnitudes (magnitude is determined by the star's absolute brightness and its distance from earth) (p. 68) |
| CCD camera sensitivity | Charge Coupled Device cameras. advantage- can rapidly capture images that do not require chemical photographic processing and can be analyzed directly with a computer (p. 62) |
| Prime hour circle | The starting line for a right ascension - a line passing through the celestial poles and a point called the vernal equinox (p.66) |
| Reflector Telescope | replaces the light-gathering objective lens from the refratcor telescope with a mirror. avoids chromatic abberration& side reflection/absorption that can occur from the large glass lens of a refractor.includes Newtonian and Cassegainian reflectors p. 57 |
| Refractor telescopes | uses only a lense to magnify an image. uses two lenses- an objective (light gathering) and and eyepiece or ocular (magnifying) lens (p. 55) |
| Apparent magnitude | ? |
| Absolute brighness | The actual amount of light that a star emits (p. 68) |
| Relative brightness | determines the magnitude of a star and is based on an original scale system established by Hipparchus based on how bright a star is relative to other stars. we now know this takes into account a star's distance from earth and absolute brightness.(p.68) |
| Radio telescopes | consist of a large parabolic "dish" that reflects radio waves emitted by a star to a focal point, where a special receiver picks up the desired signals and records their intensity (p. 60) |
| Nonoptical telescope | a radio telescope is a nonoptical telescope as they do not require visible light. (p.60) |
| Altazimuth | A type of telescope mount with separate controls for horizontal and vertical motions. (p.61) |
| Alpha | ? |
| andromeda | A galaxy which is over 2 million light years away (p.69) |
| Chromatic aberration | a color distortion which occurs when various colors of light are refracted differently in a refractor telescope (p.56) |
| Composite telescope | A telescope that uses both mirrors and a correcting objective lens to gather light. has characteristics of both a refracting and a reflecting telescope. (p.59) |
| Gnomon | an ancient devise to help astronomers determine the position and motion of the heavenly bodies. it was an upright stick or pole or column of stones or pyramid or tall stone pillar which cast shadows in sunlight. (p.53) |
| meniscus mirror | a reflector telescope mirror design where the missor is made of glass so thin that it needs computer-controlled actuators to keep it in the proper shape. (p. 59) |
| honeycomb mirror | a reflector telescope mirror desigh which uses a process called spin casting to produce a single-piece glass mirror over a honeycomb-shaped structure. allowed for bigger and more powerful telescopes begin in the 1990s (p.58) |
| segmented mirror | reflector telescope mirrors composed of 36 aluminum-coated metal mirrors that fit together like a hexagonal(six-sided) tiles to make a large mirror.segments must be mounted on precision actuators for fine adjustments of position. (p.58) |
| computer controlled mirror actuators | a bed of sensor-controlled actuator that constantly push or pull on the meniscus mirror in a reflecting telescope. it also supports the weight of the huge mirror. (p.59) |
| quadrant | A handheld navigational instrument used to measure a star's angular position above the horizon. it has a 90 degree arc with a movable sighting arm. (p. 54) |
| MIlky way | the galaxy that our sun and our solar system are in. It is approximately 100,000 light years across. (p. 69,74) (one galaxy may contain millions of stars) |
| Nebula | is singular (one) for nebulae - clouds of gas and/or dust. there are at least 5 distinct kinds of nebulae |
| November parallax | parallax is the apparent shift of nearby stars among farther stars as the earth's position changes (p.45) |
| Proper motion | one part of a star's real motion. it is the movement across the sky as we see it. this motion is very small and difficult to detect especially in the short term. (p.70) |
| Radial motion | part of a star's real motion.The movement directly toward or away from us.Even more difficult to detect than proper motion since does not cause the stars to change their position. finally detected by examining different wavelengths in the stars light p70 |
| Resolution | The aability of a telescope to bring out details in an image. determined partly by the quality of the glass of lenses and/or mirrors. but MAIN factor is the diameter of its objective lens or mirror. (p56) |
| Quasars | quasi-stellar-object(QSO)very mysterious celestial objects that do not fit neatly into accepted evoltionary models. faint starlike objects appearing to be less bright than their distance suggests. emit more energy than an entire galaxy but appear dim.p78 |
| Dark Nebulae | clouds of interstellar dust that have no nearby source of heat or light and so neither radiate nor reflect energy. block visible light frequencies from objects behind them (p.78) |
| Galaxy | consists of millions of stars. the MIlky Way is ours and astronomers believe it is a flat disk of stars with extending spiral arms. Galaxies have different shapes elliptical, barred spiral, spiral, irregular(p.74) |
| Cepheid variable | a type of star that changes in brightness regularly, apparently because it expands and contracts on a regular basis. grows=more light=brighter. shrinks=contracts=less light=dimmer. example Delta Cephei (p72) |
| Supernova | occasionally a star may increase its brighness by twenty magnitudes or more in an explosion that practically destroys the star. This type of exploding star is called a supernova (p.73) |
| Star cluster | look like stars but are not. 'fuzzy' points of light. first described and catalogued by Charles Messier. when several stars near each other have the same proper and radial motions. can be open or globular (p.74) |
| Celestial equator | divider between the northern and the southern half of the heavens - the plane of the earth's equator projected into the sky. (p.66) |
| Light year | a measure used to express the distances to the stars. it is the distance that light travels in a year, about 9.5 trillion km (5.9 trillion miles.) (p69) |
| supergiant | stars which are much larger than our sun. example Betelgeuse, brightest star in constellation Orion, red star 500xs larger (p.71) |
| Stonehenge | A ring of large stones in England which may have been an early solar observatory for determining celestial events such as solstices and equinoxes. (pp. 53-54) |
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